Telephone system



QUNNDD I m Thumas F. Bro ulcer T. F. CROCKER- TELEPHONE SYSTEM Original Filed March 14, 1929 mls June 2, 1931.

Patented June 2, 1931 own-1o srArE-s morass orl-ficaii} THOMAS E. onooknn, or CHICAGO, rumors, nssienon. To nnsnnvn HOLDING? c0111 PANY, QF- GHICAGO,' IT.-LIZ TGIS,ZA CORPORATION; OF DELAWARE.

TELEPHONE sYsrnn Original application filed applicationfiledMarch 28,

This invention relates to telephone; sys temsin general; but is concerned more particularly w-ithtone generating apparatusfor use in. such systems.

The accompanying drawing discloses the invention in connection with a: small automatic telephone-exchange system. The-in vention is shown in'this particularembodi ment only for convenience of' description, and it is. tobe-understood that it can be used equally well with other systems either largeor small and of either the manual or automatic type.- r

The features of the telephone system dis; closed inthe drawing are claimed in my Patent, No. 1,77 6,653, granted Sept. 23, 1930, of which this application is a division; The features which relate specifically to the tone generating apparatus comprise the subjectmatter of this divisional application. I

Referring now to the drawing, trunk equipment TRis individual to the trunkand associated therewith is the common equipment including night. alarm apparatus NA, opera tors telephone set, OTS, andring-back tone generator RBT. Line switchLS, also indi vidual to the trunk, is an ordinary rotary type line'switch whosewipers'move only in a forwarddirection and have no normal or home"position. Line switch'LS, together with other similar line switches of" the P. A; X., have access to theregular P.'A. connectors such as. C, which in turn have access to the various P. A. X. subscribers" lines of which that terminating inv substation T'is shown. Connector G maybe of the same general type as the connector shown in Fig. 2; of United "States Patent No. 1,175,119 to A. H. Blessing,issued March 14, 1916. Substation T is an ordinary automatic substation set comprising the usual talking, signalling, and impulsing instrumentalities. V

The operation, briefly stated, is as follows: Vhena call from the central oflice is ex tended tothe P. A. X., over the trunk, a signal'at the attendantsposition is operated. Theiring-back tone apparatus is alsozoperated and places a characteristic tone on the trunk toinform the calling subscriber or March 14, 1929, Serial No. 346,861. Patent No. 1,776,653; namedand' this 1930. Serial 170,439,555 7 switch LS in the P; The lineswitcli further extends the connection to an; idle connector suchas Cl The attendant then dials the number ofthe wanted PTALXL station The connector signalsthe'wanted station in the usual manner and when the called station answers reverses batteryback over the'calling trunk. After dialling, the I attendant restores key K to normalor may operate thekeyto the left to'listenin on the trunk; The attendant; must not hang up the receiver until the called station an-- swers. When the connector reverses battery, an additionalz locking circuit for the trunk equipment is completed, thereby placing control of the release with the called station. lVhen the attendant is assured that the call-has been answered; the attendants receiver maybe replaced or othercallsmay be handled. lVhen the called station dis connects, the locking circuit for the trunk equipment is opened and the equipment releases.

Having briefly" described the operation and the apparatus involved, a detailed description of the operation will now be given; It will be assumed'that a calliis extended to the P. A. X. from a common battery manual central ofi'ice; When theoperator'plugs in, a circuit is completed by way'ofthe opera tors cord circuit (not shown), conductor 2 of the trunkfupper left-hand winding of repeating coil R, upper windingofirelayi 11, condenser. 4, lower left-hand. winding of repeating coil R, conductor 3,.back to theop; erators cord circuit, The operator then projects ringing current outon the trunk whereupon relay-:11 operates and at armature 14 completes the. locking circuit'for its lower winding. This locking circuit may be to light. At armature 34 relay 31 also closes a circuit from battery by way otarmature 34 and its working contact to the night key which, however, is operated onlywhen the attendant is absent from the position; the

night key being normal, noaction takes If the night key is operated, the

place. buzzer will audibly signal the attendant.

Relay 51 also operates in series with relays n and 31 and at armature 56 completes a circuit for relay 52 including resistance 61. Relay 52 operates-and at armature57 closes a circuit for relay 53. Relay 53 is of the same general type as the relay shown in Fig. 1 of United States Patent No. 1,641,256 to J. Erickson, issued September 6, 1927. WVhen its circuit is closed, relay 53 actuates its armature 58. Spring 64 is rigidly fixed -at its'upper end 65 and at its lower end is fitted with a weight 63. 5 At the pointbetween the fixed end and the weight is a small projection or contact 66 with which a corresponding contact on armature 58 engages when relay 53' is energized. The engagement of the two contacts starts spring 64 tovibrating as a pendulum with the axis at the fixed end 65. As armature 58 remains in actuated position, it tends to damp the vibrations of spring 64. The amplitude of the vibrations gradually decreases and the frequency gradually increases, the change in frequency being more marked as the amplitude approaches zero. The contacts between the armature and the spring remain closed for gradually increasing intervals with each cycle of vibrations. y r The closure of the vibrating contacts com.- pletes a circuit for slow-acting relay 54. This relay hasa high impedance and when its circuit is closed for very short intervals does not actuate its armature. WVhen the closed circuit interval increases sufiiciently, the relay energizes and maintains its armature in operated position for the remainder of the period of vibration of spring 64. At armature 59, the tone lead is connected to a point between the relay and'the vibrating contacts and the remainder of the vibrations serve toproduce a tone therein. These vibrations persist for a short time after relay 54 has operated and the tone produced is transmitted back by way of armature 59, condenser 55, armature '14, lower winding of relay 11 to battery. 7

Relay 54 also short circuits'the windin of relay 52 at armature 60. Relay 52 which is also slow acting deenergizes after, a short interval and opens the circuit of relay 53 which also deenergizes. The deenergization' of relay 53 separates the vibrating contacts 66, thereby stopping the tone (assumingthat nroves the short circuit from relay 52. Re

lay 52 again energizes andstarts the cycle of operations as previously described as long as relay 51 remains energized;

As was previously stated, the upper and lower windings'of relay 11 are inductively coupled. The tone' current flowing periodically in the lower winding is induced in the upper winding -Which is bridged across the trunk. The subscriber or, operator at the, central olfice on hearing this tone, which is very similar to the ring-back tone commonly usedin automatic telephone systems, is thereby informed that the call has been extended to the P. AQX. a

On noting the lighted condition of lamp L, the attendant answers by lifting receiver RE from the switchhook and by operating key K to the left,thereby connecting the receiver RE '7 in telephonic connection with the trunk by way of the right-hand windlng of repeating coil R. The operation of key K also places a short circuit around condenser 4 and relay 11 and around condenser 5, which closes a direct current path over trunk conductors to give the operator answering supervision, and improve the transmission, and also opens the circuit of the lower winding of relay 11 and the ringback tone equipment. Relays '11 31, and

51 deenergize, thereby stopping the operation of the ring-back tone apparatus and extinguishing-lamp L. The attendant then converses with the central office operator or subscriber to determine the wanted partyat the P. A. X. It will be noted that in removing the receiver from the hook a circuit was closed from groundbyway of the switchhook, transmitter, right-hand winding of induction coil IO, winding of relay 32 to bat-j tery. Relay 32 operates and at armature 35 closes a circuit to the trunk equipment, the utilityof which will be described later on.

of the P. X. subscriber'wanted; the attendant operates key K to the right, there- After ascertaining the number orthe name by closing an obvious circuit for the lower winding of relay 13, disconnecting the talks ing leads from the repeating coil and clos ing a circuit for calling device CD. Relay 13 operates and at armature 18 closes a locking circuit for its lower winding, including armature 35 of relay 32. At armature 19 a circuit is closed. for the upper winding of polarized relay 12, which does not operate, however, over its upper wind-o ng alone. v.Att armatnres lfiand ZO-calling device CD is; bridged. across a the; trunk; eon;- duotorsrleading; toline switch LS,.t.he cir+ cult of; which maybe traced as follows:

battery,.winding of relay. 72,. armature 74 and: its resting; contact, armature; 16; upper right-hand operated: contact Oi key K, 0011-. tacts of calling device(1D,.lowercrightehand operated contact, of key. armature 20, armature. 76 and its; res ing; contact to ground, Relay 72 operates overthesabovetraced circuit and. at armature 7:7 completes a circuit for relay 7 1. and .lnotcr magnet? 3 inseries and at. armature; 78c.onnects tes wiperv 81 to the junction of: relay 71 and the motor; n1agne t.- lnicase the wipersgof: the line switch. are standing on: a: busy: trunk, w-iper- 81 will. find a; ground. An operating circuit. for therotary magnet} may be; traced from ground, wiper 81., armature 7 ,5: and its resting ntachfarmature 78., interrupter springs, winding of. rotary. magnet: 7 3 to battery. Rotary magnet 73, on operating, opens its owni circuit. at: the, interrupter springs and on. deenergizingastepsthe wipers, ahead.- to. the next: set of: contacts. This cycle of operation: is: repeated as. longas wip r: 81.; ncounters; a; grounded Contact. Relay 71. is; prevented from operating. at this time, being shuntedout; by the ground onthetest wiper. Whenan idle. contactjis found, wiper-81 will not encounter aground, and relay 7 l will, therefore, operate over the. previously traced circuit including the winding of rotary magnet 73h The: rotary magnet, however, will not operate; in series with relay 71,. dueto the: high: resistance of that; relay. Assuming; thatythe trunk comprising; conductors 82-84 leading; 'to connector C is the idle trunk selected, re: lay. 71., on operating, connectsthe, impulsing circuit throughfby way ofarmatures 745- and 76*and their working; contacts, wipers. 79 and 80, conductors 82- and. 83., to the. line relay: of connector Relay. 711 alsodisconnects the; test wiper from the; junction with the rotary magnet; and connects it: in series: with; the. relay 71. so that; when, the connector returns a ground over the release trunk, relay 71, will remain locked inopere atedpositicn.

Relay 71 also disconnects relay 72 from the trunk, and thisrelay,b.eing. slow acting, will maintain its armature'sn in; operatedposition. for' a short: time thereafter, provide ing a holding ground for-relay 71' until-the connector hashad time to return-the hold-;-. ing ground over the test wiper; The at tendant now dials-thedigits'of. the called P. A. X. station, operating connector G' in the usual way to step its wipers- 85-87 into engagement with the calling. line which will be assumed to be that comprising conductors 91 and 92 extending fro'm substation T and terminatingoncontacts 88 and-89s l hea connector signals the; called station in the well-known 'manner, and when the called. subscriberxanswers. reverses battery back. over thewtrunk in the, usual manner; "YAifter dialling-the: digits ofthe wanted station, thetattendant-will: restore keyv K to normal or operate it togtheleft, ,Thefcallingydey-ice GD. iSatllBIl. disconnectedfrom the trunk; and; the; holding circuit; for the con:- nectorg. is transferred tothe. loopinclud-. ing" the; right-hand: windingsqof repeating coil R and the.- lowentwinding of polarized relay 12.: lielayl2jdoesxnot. operate at this time, as battery. flows. inthelower winding inc-such a direction that, thetwo windings opposeeach-other; When the called; station. answers. the connector: reverses battery 3 as previously. mentioned; and,..the:- current. fiow being-"reversed. in; the. lower: winding of polarizedrelay. 12,- the two windingsi assist eachother and relay 12: operates. Relay l2 closes: a holding circuit for the upper winding of. relay. 13? at: armature 15'. The attendant: will normally-throw'key; to.-t'he left and listen in on the. trunk until: the called party answers; or, if: there areother callsvtoi'be attended to,..ke.y; maysbe restored tofnormal 'and the. other calls. at-

tended to- :WVhen the attendantis assured thereby opening the'oalledilineiloop Connector C will reverse battery over the" trunk back to no'rmal an'drelay 12wil'lzdeenergize and open the circuit of: relay .13; Relay-13 will then deenergize and open the holding l'oop to theconnector, thusfreleasing; the

lineswitclr-ancl the connector. inthe usual manner. The'equipment in the: P A. will restore to normal and willbe immediatelyavailableffor another call; The central office; subscriberor operator is thus 3:;

unable to holdupfthe connection in the P;

A; X. It will be jno'ted thatthe P. A. X. I

equipment will" not release it until the attendents receiver -is 1 replaced on the switch- In the foregoing description it: was assumed that the-callwas extended from a common battery manual central oflice. It is; obviou's;that-similar calls may be' ex tended from magneto manual central ofiices I 1' or from automatic central offices, the only requirement being that ringing currentbe projected. on the trunk. It isalso obvious thatf the attendant will not be=requ1recl to learn any complicated method of operation orbe required to watch a confusing number of supervisory signals- 1 Having described the invention, that closing saidcontacts, a tone circuit including said contacts, and a slow-to-energize re lay actuated by impulses produced at said contacts for closing said tone'circuit.

3. In a tone generator, means for producing a series of impulses of gradually increasing'duration, a relay adjustedtorespond to said impulses when they become of a certain duration, and a tone circuit closed by said relays over which the remaining im-.

. pulses are transmitted.

4. Ina tone generator, a relay having con tact members for closing a circuit when the relay is energized, a weight attached toone of said contact: members tocause. the same to vibrate when the relay is energized, said member vibrating with constantly diminishing amplitude, a second relay operated under control. of said contact members when the amplitude'of the vibrations decreases to a certain point, and means controlled by said second relay for'opening the circuitof said firstrelay. a i l r .5. In a tone generator, a relaylhaving contact members for closing a circuit when the relay is energized, a weight attached to one of said contact members to cause the same to vibrate when the relay is energized, said.

member vibrating with constantly diminishing amplitude, a circuit including a second relay and said vibrating contact member, said-secondrelay operating whenthe amplitude of the vibrations diminishes to a certain point, and a tone lead connected to a junction between said vibrating contact member and saidsecond relay responsive to the operation of said second.relay.

. 6. In a tonegenerator comprising a plurality of relays energizingand deenergizing continuously in self-interruptedcycles, a re-' lay having contact members for closing a circuit when the relay is energized, a weight attached to' one of said contact members to cause the same to vibrate when the relay is energized, said membervibrating with constantly' diminishing amplitude, a tone lead, and means for connecting said tone lead to said vibrating contact members at each operationof said relay whenthe amplitudeof the vibrations has diminished to a certain point:

val.

' 7. Ina tone generator, a starting relay, a tone relay-equipped with'vibratingcontacts for. generating a characteristic tone,-a plurality of interrupterrelays, a lead over which saidstarting relay is energized, means 9 mined stage ofthe' cycle of operations of said tone relay and said interrupter relays. 8. In a tone generator, a relay having contact members for closing a circuit when'the relayis energized, a weight attached to one of said contact me'mbers" to cause the same to vibrate when the relay is energized, said member vibrating witha constantly increasing frequency,and a relay operated under control of said contact members when the frequency of the vibrations increases to a certain point. p r 9. In a tone generator, a'relayhaving contact members for-closing a circuit when the relay is energized, a weight attached to one of said contact members to' cause the same to vibrate when the relay isenergized, said member vibrating with constantly diminishing amplitude and constantly increasing frequency, and a relay operated under control of said contact members When'the'amplitude and frequency of the vibrations reach a predetermined value.

l0. In a tone generator, a contact members for closinga'circuit when the relay is energized, a weight attached to one of'saidcontact members'to cause the same to vibrate when the relay is'energized, said member vibrating with constantly increasing frequency, and a tone circuit connected to said vibrating contact members when the frequency of thevibrations reaches aLpredetermined value. f

I 11. In a tone generator, a relay, contact springs forfsaidrelay, a weight attached to one of said springs tocause'the same to vibratei for an interval after the relay is energized and'intermittently-close thespring contacts, and a tone circuit connected to said 1 spring contacts during said vibratinginter- -12."- In a tone generator, a relay adapted when energized topermanently attract its armature, a weighted member set. 'in-vibrationi responsive to the *attraction "of said armature and adapted to vibrate for'a definite interval thereafter whilethe relay re mains energized, and a tonecircuit inter mittently closed b ed spring adapted to start vibrating responsive to the. energization of said relay and to V vibrate with constantly decreasing ampli relay having I y said member during its vlbratmg nterval.

amplitude of vibration of said spring dimin- I ishing to a predetermined value.

In witness whereof, I hereunto subscribe my name this 21st day of March, A. D. 1930.

THOMAS F. CROCKER. 

